CVE-2026-43067Critical· 9.8▾ MidnightIn the Linux kernel, the following vulnerability has been resolved: ext4: handle wraparound when searching for blocks for indirect mapped blocks Commit 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") restri…
▾ Midnight zone — Critical, or high with PoC / in-the-wild
impact 53.9 · likelihood 0.1 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.
Exploit-prediction probability, daily snapshots since Oct 16.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CVEORG
0.7%
Last analysed / modified upstream
In the Linux kernel, the following vulnerability has been resolved:
ext4: handle wraparound when searching for blocks for indirect mapped blocks
Commit 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") restricts what blocks will be allocated for indirect block based files to block numbers that fit within 32-bit block numbers.
However, when using a review bot running on the latest Gemini LLM to check this commit when backporting into an LTS based kernel, it raised this concern:
If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal group was populated via stream allocation from s_mb_last_groups), then start will be >= ngroups.
Does this allow allocating blocks beyond the 32-bit limit for indirect block mapped files? The commit message mentions that ext4_mb_scan_groups_linear() takes care to not select unsupported groups. However, its loop uses group = *start, and the very first iteration will call ext4_mb_scan_group() with this unsupported group because next_linear_group() is only called at the end of the iteration.
After reviewing the code paths involved and considering the LLM review, I determined that this can happen when there is a file system where some files/directories are extent-mapped and others are indirect-block mapped. To address this, add a safety clamp in ext4_mb_scan_groups().
Linux >= 9d89b9d55e25cb340c5b4b769876edc551b7a9ff < f89bba144938921a2249237ad04a0183ff3f8930Linux >= 1b0edd6022a3f44ce87fea9959a9310f4628fbea < 83170a05908b6cf2fb3235d3065bf613ff866f3cLinux >= 9eea2f57d11b30049ff996ac3eff6e0dc8089e5f < 4bec4a498ce86314d470ae6144120461f2138c29Linux >= 34c803edc0b3365a42efcf9815acab63b4cf54e0 < 12624c5b724a81e14e532972b40d863b0de3b7d1Linux >= 321ed8d559c951e71ad2d2d69a4cf0445644e865 < 2a368ccddfc492a0aa951e2caef2985f20e96503Linux >= 4865c768b563deff1b6a6384e74a62f143427b42 < bb81702370fad22c06ca12b6e1648754dbc37e0fLinux 16fce6b6c0b247258c6c217fce5a48abf50f6964Linux >= 5.15.203 < 5.16Linux >= 6.1.167 < 6.1.168Linux >= 6.6.130 < 6.6.134Linux >= 6.12.77 < 6.12.80Linux >= 6.18.14 < 6.18.21Linux >= 6.19.4 < 6.19.11Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
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